Projector display comprising light source units

ABSTRACT

A projection display apparatus employing organic EL elements is presented that is light in weight, is small in size, and can be practically implemented. In particular, the apparatus suppresses light-emission performance degradation caused by generated heat, thereby extending useful life, stabilizing brightness, and securing continual maximum brightness. The apparatus comprises; liquid crystal panels  12 R,  12 G, and  12 B; light emitting units  13 R,  13 G, and  13 B, positioned at the back of the liquid crystal panels and provided with organic EL elements as light emitting layers; and cooling bodies  14 R,  14 G, and  14 B, positioned at the back of the light emitting units, for dispersing the heat generated by the light emitting layers. The cooling bodies  14 R,  14 G, and  14 B may, for example, be electronic cooling elements that employ the Peltier effect to absorb and radiate the generated heat. Alternatively, the cooling bodies may be configured as heat-dispersing fins that guide and disperse generated heat.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention concerns a projection type displayapparatus that comprises light source units comprising cooling means andlight emitting units that include light emitting layers comprisingorganic EL (electroluminescence) elements, wherein the light emittedfrom the light emitting units is guided to liquid crystal panels, andthe images displayed on the liquid crystal panels are enlarged andprojected by a lens or lenses.

[0003] The present invention also concerns cooling control technologyfor cooling the light emitting units that employ light emitting layersmade up of organic EL (electroluminescence) elements and that are usedin various fields. More particularly, the present invention pertains toa light source apparatus formed by adding temperature detection means orelapsed time measuring means to light source units comprising lightemitting units and cooling means, and to a method and apparatus forcontrolling a light source apparatus that controls the cooling means bythe temperature detection means or elapsed time measuring means in thelight source apparatus.

[0004] 2. Description of the Related Art

[0005] In recent years, with the amazing advances being made insemiconductor technology, various electronic display devices other thanCRT displays are being developed and turned into marketable products.One of these which is drawing much attention is the projection displayapparatus, a technology that is advantageous in terms of lower powerconsumption and lighter weight.

[0006] One type of such a projection display apparatus that is known isthe liquid crystal projector wherewith images on a liquid crystal panelare enlarged and projected by a projection lens onto a reflective ortransmissive screen and thus displayed. One example of such a liquidcrystal projector is diagramed in FIG. 31.

[0007] The liquid crystal projector diagrammed in FIG. 31 comprises alight source lamp unit 202 inside a cabinet. Electrical discharge lampssuch as metal halide lamps, or halogen lamps, are used in the lightsource lamp unit 202. The light emitted from this light source lamp unit202 is guided via a mirror 203 to dichroic mirrors 204 and 205, wherebyit is separated into red light green light, and blue light. Of the threecolor components into which the light is separated, the red light passesby way of a mirror 206 to a red displaying liquid crystal panel 209, thegreen light is led directly to a green displaying liquid crystal panel210, and the blue light is led by way of mirrors 207 and 208 to a bluedisplaying liquid crystal panel 211.

[0008] The images displayed on the three liquid crystal panels 209through 211, respectively, are illuminated by their respective colors,and this light is combined by a dichroic prism 212. The combined lightis enlarged by a projection lens 213 and projected, in enlarged form, ona reflecting screen (not shown), for example.

[0009] With a liquid crystal projector in which a light source lamp unit202 such as this is used, however, the light emitted from the metalhalide lamp or halogen lamp must be radiated with good parallelism ontothe liquid crystal panel. For this purpose, as diagrammed in FIG. 31, itis necessary to provide the light source lamp unit 202 with a reflector202A having a rather large aperture. This constitutes a serious problemin that it makes it difficult to meet the demand for lighter weights andsmaller sizes in the overall projector.

[0010] As is depicted in FIG. 31, moreover, it is preferable that thelamp in the light source be cooled. The larger the capacity of the lamp,in fact, the higher must the cooling capability of the cooling fan be.

[0011] In the case of a so-called triple liquid crystal projector,moreover, in which three separate liquid crystal panels are provided forthe red, green, and blue colors, as described in the foregoing, a lightdividing optical system is necessary to take the light emitted from thesingle-lamp light source and divide it into the colors on the threeliquid crystal panels. This makes it even more difficult to achieve thedesired reduction in weight and size.

[0012] A first example of the related art is now discussed.

[0013] In recent years, in an effort to break out of this dilemma, theuse of organic EL elements as the light emitting unit has been proposed.This reflects the fact that many reports have been made of light of highbrightness being emitted by EL elements using an organic thin film forthe light emitting layer. These light emitting units are thin planarlight sources in which are formed an electric-field light-emission(electroluminescence=EL) layer consisting of an organic thin film.Compared to inorganic EL elements, organic EL elements can operate atlow voltage and provide high brightness. Thus they are believed to bewell suited for use in enlarging-projection type projection displayapparatuses, and much research is being focused on the practicalimplementation of such devices.

[0014] An example of a triple liquid crystal projector in which suchorganic EL elements are used as the light source unit is diagrammed inFIG. 32 and 33. In the liquid crystal projector depicted in thesedrawings, light source units 224, 225, and 226, in which are usedorganic EL elements that emit red, green, and blue light, respectively,are positioned, respectively, behind and in close proximity to threeliquid crystal panels 221, 222, and 223, which display red, green, andblue colors. Item 227 is a dichroic prism, and 228 is a projection lens.An example of this type of projection display apparatus is disclosed inlaid-open patent application (Tokkai) S51-119243 [1976] (gazette).

[0015] Even with such a triple liquid crystal projector such as this,however, in which organic EL elements are used as the light source unit,the organic EL elements produce heat when they are driven, and thusrequire cooling.

[0016] A second example of the related art is now discussed. Onepossible means of forcibly cooling such organic EL elements as these isto employ electrical cooling elements that utilize the Peltier effect.

[0017] Nevertheless, in the liquid crystal projector of the firstexample of the related art depicted in FIG. 32 and 33 and describedabove, a planar light emitting unit in which organic EL elements areused is employed, thus making it possible to achieve smaller sizes andlighter weights, but some unresolved problems remain, as noted below.These problems present obstacles which prevent this technology frombeing practically implemented.

[0018] In the first place, even though these are called organic ELelements, they produce heat when they are driven, and this emission ofheat causes the light emitting performance to gradually deteriorate,shortening the useful life of the elements.

[0019] Furthermore, if the light emission performance of a light sourceunit in which organic EL elements are used has fallen below allowablelimits, then one would like to be able to replace only the light sourceunit. In a color-displaying triple liquid crystal projector, inparticular, light source units are provided for each of the three liquidcrystal panels, so the number thereof is high. A deterioration in theperformance of one or two of the light source units destroys the colorbalance of the displays on the screen, so the effects thereof are great.In such cases, it would be economical to be able to simply replace onlythose light source units which have reached the limit of their usefullife. Previously, however, no structure has been proposed for such lightsource units which would make them independent and easily replaceable.This has obliged repair personnel to go to the great trouble of changingout light source units on boards on which they are mounted.

[0020] When making such replacements, it is very important not only toinsure the electrical connection with the light source unit afterreplacement, but also to insure that it has been restored to theprescribed optical position. If the orientation or position of thereplaced light source unit is off, the way in which light strikes theliquid crystal panels will be altered, the picture on the screen may bepartially darkened, and the display performance may be degraded.

[0021] Another important aspect to consider when making replacements isrightly judging when exactly to make the replacement. If suchreplacement is made late, brightness may be reduced, and viewers mayhave to put up with pictures that exhibit distorted color balance.Conversely, if the replacement is made too early, that will adverselyaffect economy. In other words, it is important to judge when the righttime to make the replacement is. Previously, however, no effective wayto remedy this had been proposed.

[0022] Furthermore, the light emitted from planar light source units inwhich organic EL elements are used is not necessarily parallel, and whenit strikes a liquid crystal panel it exhibits the property of widelyspreading out. For this reason, the light emitted from the light sourceunits contains much wasted light that does not contribute to the displayof the image on the liquid crystal panels, by which measure thebrightness of the displayed picture deteriorates. Moreover, efforts toraise the display brightness to compensate for this wasted light resultin recklessly raising the light emission output of the organic ELelements, which leads to a vicious cycle in which the heat generateddegrades the light emission performance and leads to even more severeshortening of useful life.

[0023] In terms of enhancing the efficiency with which light is emittedfrom this light source unit, transparent glass plates placed on theemission side of the organic thin films making up the organic ELelements play an important role.

[0024] Conventionally, however, these plates have been of a simple formin which both front and back surfaces are parallel.

[0025] With the first example of the related art discussed above, it hasbeen very difficult to achieve a practical projection display apparatusdue to the many problems cited.

[0026] With the second example of the related art, moreover, when lightemitting units comprising organic EL elements, and cooling means, areemployed, and electronic cooling elements are used to cool the organicEL elements, if one begins driving the cooling elements simultaneouslywith lighting the organic EL elements, the temperature of the organic ELelements will rise before they are cooled, whereupon the organic ELelements will be thermally degraded, which constitutes a problem.

[0027] When the cooling elements are activated first, and the organic ELelements are lighted subsequently, the organic EL elements are cooledbefore they emit light, causing dew to form. This also constitutes aproblem.

[0028] Furthermore, when the use of the light source apparatus isdiscontinued, if the timing between extinguishing the organic ELelements and stopping the cooling elements is improper, either theorganic EL elements will suffer thermal degradation or dew will beformed. This constitutes yet another problem.

[0029] A first major object of the present invention is to provide aprojection display apparatus in which are employed light source unitscomprising cooling means and a light emitting unit comprising organic ELelements, which is light in weight, is small in size, and can bepractically implemented.

[0030] One specific object of the present invention is to make itpossible to prevent degradation in light emission performance caused byheat generation in the organic EL elements, thereby making it possibleto increase useful life, stabilize brightness, and secure maximumbrightness continually.

[0031] Another specific object of the present invention is to establishindependent light emitting units comprising organic EL elements, suchthat they can easily be replaced so that their electrical connection andoptical positioning are secured, and so that the replacement operationis rendered more efficient and maintenance and inspection are madeeasier.

[0032] Another specific object of the present invention is to make itpossible to easily judge when replacements should be made, thus makingit possible to insure high picture display quality, and renderingmaintenance and inspection easier.

[0033] Another specific object of the present invention is to enhancethe efficiency with which light strikes the liquid crystal panels.

[0034] Another specific object of the present invention is to enhancethe efficiency with which light is emitted from the light source unit bythe organic EL elements, by improving the transparent substrates onwhich the light source units are mounted.

[0035] A second major object of the present invention is to provide alight source apparatus wherewith it is possible to prevent both thermaldegradation in the organic EL elements and the formation of dew,together with a method and an apparatus for controlling the light sourceapparatus.

SUMMARY OF THE INVENTION

[0036] In order to achieve the first object cited above, the projectiondisplay apparatus according to the present invention comprises:transmissive liquid crystal panels that display images; light sourceunits that are positioned on the back side of the liquid crystal panelsand that comprise light emitting units provided with organic EL elementsas light emitting layers and cooling means provided in the lightemitting units for radiating heat generated by the light emitting units;and a projection lens positioned in front of the liquid crystal panelsfor enlarging images displayed on the liquid crystal panels andprojecting them onto a screen.

[0037] For example, the cooling means exhibit a structure wherein thereare electronic cooling means utilizing the Peltier effect positioned atthe back of reflecting electrode layers positioned at the back of thelight emitting units, and thermal conductors that conduct generated heatare interposed between the reflecting electrode layers and the lightemitting layers.

[0038] For example, moreover, the cooling means comprise cooling bodiesprovided with heat-radiating fins that conduct and radiate the generatedheat, provided at the back of reflective electrode layers positioned atthe back of the light emitting layers, and sealing substrates that sealoff the portions of light emitting film structures that include thereflecting electrode layers, and that integrate the sealing substratesand the cooling bodies.

[0039] Also, the surface areas of the heat-radiating fins of the coolingbodies are formed so that the center portions of the light emittingunits are larger than the end portions.

[0040] For example, moreover, the organic EL elements are elements thatgenerate white light.

[0041] For example, moreover, the liquid crystal panels comprise threeliquid crystal panels that separately display images in red components,green components, and blue components, the organic EL elementscomprising three organic EL elements that separately generate red,green, and blue light, exhibiting a structure wherein a dichroic prismis interposed in the optical path between the three liquid crystalpanels and the projection lens.

[0042] In order to achieve the first object and the specific objectsnoted above, the projection display apparatus to which the presentinvention pertains comprises transmissive liquid crystal panels thatdisplay images; light emitting units positioned in back of the liquidcrystal panels and provided with light emitting layers comprisingorganic EL elements; and attachment means for attaching the lightemitting units, such that they can be freely attached and detached, toat least the portion of a base on which is mounted the liquid crystalpanels and the light emitting units.

[0043] For example, moreover, the light emitting units comprise basesthat mount both electrode layers that sandwich the light emitting layersand terminals that are electrically connected to the electrode layers,while the attachment means are equipped both with connectors that plugterminal units into the base portions, such that they can be freelyplugged and unplugged, the terminal units having mounted in them theterminals of the boards, and with guides that guide the boards in thedirection of connector plug-in, when the terminal units of the boardsare inserted into the connectors.

[0044] For example, moreover, light source units are provided whichcomprise cooling means for radiating heat generated by the lightemitting layers, and light emitting units containing the light emittinglayers.

[0045] For example, moreover, the cooling means comprise heat-radiatingfins that are provided on the back side of the reflective electrodelayers positioned at the back of the light emitting layers, whichconduct and radiate the generated heat.

[0046] Furthermore, in order to achieve the first object noted above,the projection display apparatus to which the present invention pertainscomprises transmissive liquid crystal panels that display images, andlight emitting units, positioned at the back of the liquid crystalpanels, in which light emitting layer structures having light emittinglayers made up of organic EL elements are provided on transparentsubstrates, wherein means for raising the light-emission efficiency areformed integrally on the light emitting surfaces of the transparentsubstrates of the light emitting units.

[0047] For example, moreover, the means for raising the light-emissionefficiency are microlens arrays formed two-dimensionally an thelight-emission surfaces.

[0048] For example, moreover, the means for raising the light-emissionefficiency are microprism arrays formed two-dimensionally on thelight-emission surfaces.

[0049] In order to achieve the first object and the specific objectsnoted earlier, the projection display apparatus to which the presentinvention pertains comprises light emitting units positioned at the backof liquid crystal panels and having light emitting film structures, thelight emitting layers of which are organic EL elements, provided ontransparent substrates; voltage measuring means for measuring voltageson terminals between the electrodes of the light emitting filmstructures; useful-life assessment means that assess the useful liferemaining in the light emitting film structures; and announcement meansthat announce the useful life when the useful-life assessment means haveassessed the useful life.

[0050] Here, for example, the useful-life assessment means are meansthat assess the useful life by converting the values of the voltages onthe terminals to brightness values and comparing these against referencevalues.

[0051] For example, moreover, here are comprised color-balanceassessment means for assessing the red, green, and blue color balance onthe basis of the terminal voltage values measured by the voltagemeasuring means, and color-balance correction means that automaticallycorrect the color balance on the basis of the results of the assessmentsof the color-balance assessment means.

[0052] For example, moreover, the light emitting layer structure for thelight emitting units comprises a resonator structure that selectivelyresonates and emits light of a particular wavelength.

[0053] In order to achieve the two objects noted above, the light sourceapparatus to which the present invention pertains comprises light sourceunits comprising light emitting units provided with organic EL elementsas light emitting layers and cooling means provided in the lightemitting units for radiating heat generated by the light emitting units;and temperature detection means for measuring the temperature of thecooling means.

[0054] In order to achieve the two objects noted above, the light sourceapparatus to which the present invention pertains comprises light sourceunits comprising light emitting units provided with organic EL elementsas light emitting layers and cooling means provided in the lightemitting units for radiating heat generated by the light emitting units;and temperature detection means for measuring the temperature of theorganic EL elements.

[0055] In order to achieve the two objects noted above, the light sourceapparatus to which the present invention pertains comprises light sourceunits comprising light emitting units provided with organic EL elementsas light emitting layers and cooling means provided in the lightemitting units for radiating heat generated by the light emitting units;and at least one or otter of elapsed time measuring means for measuringthe elapsed time after the start of the cooling means or elapsed timemeasuring means for measuring the elapsed time after the stopping of thecooling means.

[0056] In order to achieve the two objects noted above, the light sourceapparatus control method to which the present invention pertains is alight source apparatus control method for controlling cooling starts andthe lighting of a light source comprising light source units comprisinglight emitting units provided with organic EL elements as light emittinglayers and cooling means provided in the light emitting units forradiating heat generated by the light emitting units, and temperaturedetection means for measuring the temperature of the cooling means;wherein the organic EL elements are lighted at the point in time whenthe temperature detected by the temperature detection means reaches aset temperature, after the cooling means have been started.

[0057] In order to achieve the two objects noted above, the light sourceapparatus control method to which the present invention pertains is alight source apparatus control method for controlling cooling starts andthe lighting of a light source comprising light source units comprisinglight emitting units provided with organic EL elements as light emittinglayers and cooling means provided in the light emitting units forradiating heat generated by the light emitting units, and temperaturedetection means for measuring the temperature of the organic ELelements; wherein the organic EL elements are lighted at the point intime when the temperature detected by the temperature detection meansreaches a set temperature, after the cooling means have been started.

[0058] In order to achieve the two objects noted above, the light sourceapparatus control method to which the present invention pertains is alight source apparatus control method for controlling cooling stoppagesand the extinguishing of a light source comprising light source unitscomprising light emitting units provided with organic EL elements aslight emitting layers and cooling means provided in the light emittingunits for radiating heat generated by the light emitting units, andtemperature detection means for measuring the temperature of the coolingmeans; wherein after reducing the drive current going to the organic ELelements, the cooling means are stopped, and the organic EL elements areextinguished at the point in time when the temperature detected by thetemperature detection means reaches a set temperature.

[0059] In order to achieve the two objects noted above, the light sourceapparatus control method to which the present invention pertains is alight source apparatus control method for controlling cooling stoppagesand the extinguishing of a light source comprising light source unitscomprising light emitting units provided with organic EL elements aslight emitting layers and cooling means provided in the light emittingunits for radiating heat generated by the light emitting units, andtemperature detection means for measuring the temperature of the organicEL elements; wherein after reducing the drive current going to theorganic EL elements, the cooling means are stopped, and the organic ELelements are extinguished at the point in time when the temperaturedetected by the temperature detection means reaches a set temperature.

[0060] In order to achieve the two objects noted above, the light sourceapparatus control method to which the present invention pertains is alight source apparatus control method for controlling cooling starts andthe lighting of a light source comprising light source units comprisinglight emitting units provided with organic EL elements as light emittinglayers and cooling means provided in the light emitting units forradiating heat generated by the light emitting units, and elapsed timemeasuring means for measuring the elapsed time from the start of thecooling means; wherein the organic EL elements are lighted after acertain time has elapsed since the cooling means were started.

[0061] In order to achieve the two objects noted above, the light sourceapparatus control method to which the present invention pertains is alight source apparatus control method for controlling cooling stoppagesand the extinguishing of a light source comprising light source unitscomprising light emitting units provided with organic EL elements aslight emitting layers and cooling means provided in the light emittingunits for radiating heat generated by the light emitting units, andelapsed time measuring means for measuring the elapsed time from thestoppage of the cooling means; wherein after reducing the drive currentgoing to the organic EL elements, the cooling means are stopped, and theorganic EL elements are extinguished a certain time thereafter.

[0062] In order to achieve the two objects noted above, the light sourceapparatus control apparatus to which the present invention pertains is acontrol apparatus for a light source apparatus that comprises lightsource unite comprising light emitting units provided with organic ELelements as light emitting layers and cooling means provided in thelight emitting units for radiating heat generated by the light emittingunits, and temperature detection means for measuring the temperature ofthe cooling means, and that illuminates liquid crystal display elementswith light radiated from the organic EL elements; wherein the lightsource apparatus is controlled so that, when lighting the organic ELelements, the organic EL elements are lighted at the point in time when,after the cooling means have been started, the temperature detected bythe temperature detection means reaches a set value for lighting, and,when extinguishing the organic EL elements, the cooling means arestopped after reducing the drive current going to the organic ELelements, and the organic EL elements are extinguished at the point intime when the temperature detected by the temperature detection meansreaches a set value for extinguishing.

[0063] In order to achieve the two objects noted above, the light sourceapparatus control apparatus to which the present invention pertains is acontrol apparatus for a light source apparatus that comprises lightsource units comprising light emitting units provided with organic ELelements as light emitting layers and cooling means provided in thelight emitting units for radiating heat generated by the light emittingunits, and temperature detection means for measuring the temperature ofthe organic EL elements, and that illuminates liquid crystal displayelements with light radiated from the organic EL elements; wherein thelight source apparatus is controlled so that, when lighting the organicEL elements, the organic EL elements are lighted at the point in timewhen, after the cooling means have been started, the temperaturedetected by the temperature detection means reaches a set value forlighting, and, when extinguishing the organic EL elements, the coolingmeans are stopped after reducing the drive current going to the organicEL elements, and the organic EL elements are extinguished at the pointin time when the temperature detected by the temperature detection meansreaches a set value for extinguishing.

[0064] In order to achieve the two objects noted above, the light sourceapparatus control apparatus to which the present invention pertains is acontrol apparatus for a light source apparatus that comprises lightsource units comprising light emitting units provided with organic ELelements as light emitting layers and cooling means provided in thelight emitting units for radiating heat generated by the light emittingunits, and both elapsed time measuring means for measuring the elapsedtime from the start of the cooling means and elapsed time measuringmeans for measuring the elapsed time from the stoppage of the coolingmeans, and that illuminates liquid crystal display elements with lightradiated from the organic EL elements; wherein the light sourceapparatus is controlled so that, when lighting the organic EL elements,the organic EL elements are lighted after a certain time has elapsedsince the cooling means were started, and so that, when extinguishingthe organic EL elements, the cooling means-are stopped after reducingthe drive current going to the organic EL elements, and the organic ELelements are extinguished a certain time thereafter.

[0065] For example, moreover, the control apparatus for the light sourceapparatus is applied to a projection type projection display apparatuswhich takes images displayed on the liquid crystal display elements andenlarges and projects them by a projection lens.

BRIEF DESCRIPTION OF THE DRAWINGS

[0066]FIG. 1 is a simplified plan of a liquid crystal projector thatconcerns a first embodiment of the present invention;

[0067]FIG. 2 is a diagram depicting the way layers are laminated in alight emitting unit having an organic EL element as the light emittinglayer;

[0068]FIG. 3 is a diagram showing how a cooling body is attached ascooling means to a light emitting unit;

[0069]FIG. 4 in a simplified plan of a liquid crystal projector thatconcerns a second embodiment of the present invention;

[0070]FIG. 5 in a diagram showing how a cooling body is attached ascooling means to a light emitting unit;

[0071]FIG. 6 is a diagram showing how another cooling body is attachedto a light emitting unit;

[0072]FIG. 7 is a diagram showing how yet another cooling body isattached to a light emitting unit;

[0073]FIG. 8 is a simplified partial plan of a liquid crystal projectorthat concerns a third embodiment of the present invent ion;

[0074]FIG. 9 is a diagonal view that depicts the guide and connectorparts of FIG. 8;

[0075]FIG. 10 is a diagonal view that depicts a light emitting unitstructured so that it is can be replaced;

[0076]FIG. 11 is a simplified cross-sectional view in the A-A plane ofFIG. 10;

[0077]FIG. 12 is a simplified plan of the vicinity of a light emittingunit in a liquid crystal projector that concerns a fourth embodiment ofthe present invention;

[0078]FIG. 13 is a simplified diagonal view of the configuration in FIG.12;

[0079]FIG. 14 is a simplified plan of the configuration in the vicinityof a light emitting unit in a modification of the fourth embodimentof-the present invention;

[0080]FIG. 15 is a simplified diagonal view of the configuration in FIG.14;

[0081]FIG. 16 is a simplified diagram of the configuration in thevicinity of a light emitting unit in a liquid crystal projector thatconcerns a fifth embodiment of the present invention;

[0082]FIG. 17 in a simplified diagram of the configuration of a lightemitting unit provided without a lens array, which contrasts with FIG.16;

[0083]FIG. 18 is a simplified diagram of a microprism array thatrepresents a modification of the fifth embodiment of the presentinvention;

[0084]FIG. 19 is a simplified diagram of the configuration in thevicinity of a light emitting unit in a liquid crystal projector thatconcerns a sixth embodiment of the present invention;

[0085]FIG. 20 is a diagram for describing differences in spectrumwaveform depending on the presence or absence of a resonator structure;

[0086]FIG. 21 is a diagram for describing differences in directionalitydepending on the presence or absence of a resonator structure;

[0087]FIG. 22 is a graph that represents the relationship betweenbrightness and accumulated drive time in a light emitting unit that hasan organic EL element as its light emitting layer;

[0088]FIG. 23 is a graph that represents the relationship betweenterminal voltage and accumulated drive time in a light emitting unitthat has an organic EL element as its light emitting layer;

[0089]FIG. 24 is a graph that represents the relationship betweenbrightness and current value in a light emitting unit having an organicEL element as its light emitting layer;

[0090]FIG. 25 is a block diagram of one example of terminal voltagemeasuring and control circuitry for a light emitting unit in a liquidcrystal projector that concerns a seventh embodiment of the presentinvention;

[0091]FIG. 26 is a flowchart of CPU processing in the seventhembodiment;

[0092]FIG. 27 is a simplified cross-sectional view of the configurationof a light source in an eighth embodiment of the present invention;

[0093]FIG. 28 is-a simplified cross-sectional view of the main opticalsystem that configures a liquid crystal display apparatus in a ninthembodiment of the present invention;

[0094]FIG. 29 is a simplified cross-sectional view of a light source ina tenth embodiment of the present invention;

[0095]FIG. 30 is a simplified cross-sectional view of a light source inan eleventh embodiment of the present invention;

[0096]FIG. 31 is a simplified plan of the configuration of aconventional example of a liquid crystal projector;

[0097]FIG. 32 is a simplified plan of the configuration of anotherconventional example of a liquid crystal projector; and

[0098]FIG. 33 it a simplified diagonal view of the configuration in FIG.32.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0099] Projection display apparatuses concerning preferred embodimentsof the present invention are described below, with reference to theattached drawings. In the embodiments described below, a liquid crystalprojector is adopted as the liquid crystal display apparatus.

[0100] A first embodiment is now described with reference to FIGS. 1 to3. The liquid crystal projector diagrammed in FIG. 1 is configured as arear-projecting type of triple liquid crystal projector.

[0101] This liquid crystal projector comprises a cabinet 11. Inside thecabinet 11 are provided three liquid crystal panels 12R, 12G, and 12Bthat perform image displays in red, green, and blue, respectively,panel-form light emitting units 13R, 13G, and 13B positioned incorrespondence with the liquid crystal panels, respectively, panel-formcooling bodies 14R, 14G, and 14B positioned as cooling means for each ofthe light source units, a dichroic prism 15, and a projection lens 16.Light source units are configured by the light emitting units 13R, 13G,and 13B, and the cooling bodies 14R, 14G, and 14B. The liquid crystalpanels 12R, 12G, and 12B and the light source units (i.e. the lightemitting units 13R, 13G, and 13B, and the cooling bodies 14R, 14G, and14B) are positioned on the light-incidence side of the side surfaces ofthe dichroic prism 15 for each display color combination.

[0102] The projection lens 16 is positioned on the light-emission sideof the dichroic prism 15. A transmissive screen 17 is positioned on thelight-emission side of the projection lens 16, at a prescribed distancetherefrom. The projection lens 16 is represented as a single lens in thedrawing, but ordinarily it will be made up of a plurality of lenses.

[0103] This liquid crystal projector is classified as a rear-projectingtype. That is because it is a type wherein an enlarged image isprojected from the back side (the side where the projector is) of thetransmissive screen 17 which is of a size of about 20 inches. In aliquid crystal projection television, this screen is secured to thecabinet 11.

[0104] Here, the surface on the light-source side of each of the liquidcrystal panels 12R, 12G, and 12B is called the back or back surface, andthat direction is called the back side, while the light-emission sidesof the liquid crystal panels 12R, 12G, and 12B, respectively, are calledthe front or front surface sides, as necessary. The liquid crystalpanels 12R, 12G, and 12B are formed, respectively, by laminating asubstrate, polarizing panel, and phase contrast panel, etc., to formelements in which a sandwiched-in liquid crystal layer is electricallydriven, such that they display red, green, and blue images. The size ofeach of the liquid crystal panels, stated as a diagonal sizes may be 33mm (1.3 inches), for example.

[0105] For the light emitting units 13R, 13G, and 13B, organic EL(electroluminescence) elements are used. These organic EL elements areformed in panels and have an electric-field light emitting layerstructure comprising organic thin films that handle the emission of red,green, and blue light, respectively.

[0106] More specifically, each of the light emitting film portions ofthe light emitting units 13R, 13G, and 13B, respectively, as diagrammedin FIG. 2, comprises a glass substrate that is a transparent substrate20, a transparent electrode layer 21 consisting of a transparentelectrically conducting thin film layer formed on the glass substrate, alight emitting layer 22 consisting of an organic thin film layer thatemits red, green, or blue light, formed on the electrode layer, and areflective electrode layer 23 consisting of a metallic film that doublesas a reflective mirror, laminated so as to sandwich in the lightemitting layer. A light emitting film structure LT is formed by thetransparent electrode layer 21, light emitting layer 22, and reflectiveelectrode layer 23. The effective light emitting region of the lightsource unit is formed to have a diagonal size of 33 mm or greater, andis positioned in close proximity to the back surface of the liquidcrystal panel.

[0107] The light emitting layer 22 emits red, green, or blue light whenthe electric field is applied between the transparent electrode layer 21and the reflective electrode layer 23. For the organic materials used toform the organic thin films, a material in which a red fluorescentpigment is added to a quino-lithol-aluminum complex or the like is usedfor red (wavelength≅610 nm), a quino-lithol-aluminum complex or the likeis used for green (wavelength≅540 nm), and a zinc oxazole complex or thelike is used for blue (wavelength≅460 nm).

[0108] The light emitting units 13R, 13G, and 13B, respectively, asdiagramed in FIG. 3, are provided with a sealing substrate 24 that isbonded to the back side of the light emitting film structure LT so as toseal it off. A metal such as aluminum or copper is suitable for thematerial of this sealing substrate 24.

[0109] Each of the cooling bodies 14R, 14G, and 14B, respectively, isprovided with a thermal conductor 25 that conducts heat away from thesealing substrate 24, and with a panel-form electronic cooling element26 that is bonded to the back side of the thermal conductor 25. A liquidor metal that in a good conductor of heat is used for the thermalconductor 25. Examples of such materials are silicon grease havingoutstanding thermal conductivity and adhesives having outstandingthermal conductivity. Alternatively this may even be solder. It ispreferable that the thermal conductor be capable of withstandingtemperatures of between 100° C. and 200° C.

[0110] The electronic cooling elements 26 are elements that utilize thePeltier effect in which heat is absorbed or radiated when an electriccurrent is passed. The heat-absorbing side of the element is bondedintegrally to the thermal conductor 25.

[0111] For this reason, the heat generated by the light emitting filmstructure LT that is conveyed to the thermal conductor 25 is absorbed bythe electronic cooling element 26, and is then radiated away from theopposite side. The heat-radiating side of the electronic cooling element26 may operate by natural heat radiation, but it is preferable that theheat be radiated away more aggressively by attaching a heat sink (notshown). Heat-radiating fins, for example, are good for this purpose.

[0112] It is even more preferable, however, that a radiating-fin coolingfan (which may be a small fan) be provided in back of the heat-radiatingfins. This may be implemented either by providing individualheat-dissipating fans for each radiating fin unit, or by providing aheat-dissipating fan somewhere inside the cabinet for the purpose ofcreating air convection within the cabinet.

[0113] The operational effectiveness of this embodiment is nowdescribed. The light that is emitted from the red, green, and blue lightemitting units 13R, 13G, and 13B strikes the liquid crystal panels 12R,12G, and 12B that are positioned in opposition for each color,respectively. This incident light illuminates the liquid crystal panels12R, 12G, and 12B which display red, green, and blue images. The imagedisplay light leaving the liquid crystal panels 12R, 12G, and 12B entersthe dichroic prism 15 and is combined. This combined light is magnified10 times, for example, by the projection lens 16. This magnified lightis projected onto the transmissive screen 17. In this manner, a colorimage having a diagonal size of 330 mm (13 inches), for example, isdisplayed on the screen 17.

[0114] The heat that is radiated from the light emitting film structuresLT of the light emitting units 13R, 13G, and 13B during this display isconveyed to the cooling bodies 26 via the sealing substrates 24 and thethermal conductors 25. At the cooling bodies 26, the heat conductedthereto is absorbed, radiated, and dissipated. Thus, with this activecooling, almost all of the heat produced in the light emitting filmstructures LT, that is, in the light emitting layers 22, is dissipatedto the outside, without accumulating in the light emitting units 13R,13G, and 13B.

[0115] That being so, degradation of light emitting performance in thelight emitting layers 22 due to heat generation is suppressed, and theuseful life of the light source is lengthened. The brightness of thedisplay screen is also maintained at high levels, so that stable, brightpictures are produced.

[0116] Furthermore, a projection display apparatus is provided that canbe practically implemented, wherewith the difficulties associated withthe prior art are overcome while enjoying the advantages of lighterweight and smaller size afforded by mounting the light emitting unitsemploying organic EL elements, together with their cooling bodies, andusing the organic EL elements as light sources.

[0117] Also, the light emitting units are not limited to emitting onlythe specific colors of red-, green, and blue, as described in theforegoing. They may also commonly carry light emitting layers that emita combination of red, green, and blue light, or light emitting layersthat emit white light containing these three primary colors. In suchcases, in the configuration diagrammed in FIG. 1, one only need insertseparate wavelength filters that transmit only red, green, or blue,between the dichroic prism 15 and the respective liquid crystal panels12R, 12G, and 12B.

[0118] It is also possible combine one liquid crystal panel wherein isformed red, green, and blue color filters for each pixel together withone light emitting unit having an organic EL element structure thatemits white light and a projection lens.

[0119] It is also possible to implement a projector structure which usesa reflective screen having a size of 100 inches or so instead of thetransmissive screen. When a reflective screen is used, the images caston the screen are viewed from the same side as the projector.

[0120] A second embodiment is now described with reference to FIG. 4 and5. As with the embodiment described in the foregoing, this embodimentinvolves the cooling of light emitting units which employ organic ELelements. Configurational elements that are the same as or similar tothose described for the first embodiment are denoted by the samereference characters, and the description thereof is either omitted orabridged. (The same applies to descriptions for the third and subsequentembodiments herein.)

[0121] The liquid crystal projector diagrammed in FIG. 4 is configuredas a rear-projecting triple liquid crystal projector. This projectordiffers from the liquid crystal projector of the first embodiment inthat the cooling means for the light emitting units 13R, 13G, and 13B,in which organic EL elements are employed, are different. Whereaselectronic cooling elements were used in the first embodiment, coolingbodies that employ heat-radiating fins are used in this embodiment.

[0122] To the back surfaces of the light emitting units 13R, 13G, and13B are bonded cooling bodies 31R, 31G, and 31B, respectively, asnaturally radiating cooling means. Each of the cooling bodies 31R, 31G,and 31B is provided with a thermal conductor 25 formed on a sealingsubstrate 24, and a radiating fin unit 32 is bonded to the thermalconductor 25, as diagrammed in FIG. 5.

[0123] The radiating fin unit 32 is formed of a substance such asaluminum which is a good conductor of heat. In addition, the side of theradiating fin unit 32 opposite the thermal conductor 25, that is, theheat-radiating surface, has vertically oriented undulations (in thevertical dimension of the radiating fin units 32 in FIG. 5) consistingof a plurality of peaks and valleys formed therein so that thecross-section thereof takes on a wave form. It in preferable that aheat-dispersing fan such as was described for the first embodiment beprovided, either at the back of the radiating fins or somewhere in thecabinet 11.

[0124] Thus heat released from the light emitting film structure LT willbe conveyed to the radiating fin unit 32 via the sealing substrate 24and the thermal conductor 25, and will be dissipated by naturalradiation from the heat-radiating surface thereof. As a result, coolingwill be effected in this second embodiment also so as to effectivelysuppress the accumulation of heat generated by the light emitting units13R, 13G, and 13B. Furthermore, in this case, because the cooling meansare radiating fine, there is no need to employ an electric current, aswith the electronic cooling elements, thus affording the advantage ofbeing able to make the power supply circuit smaller.

[0125] Various modifications are possible in the shapes of the coolingbodies 31R, 31G, and 31B pertaining to the second embodiment, asdescribed in the foregoing, as are depicted in FIG. 6 and 7, forexample. The cooling body depicted in FIG. 6 integrates three of themembers described above, namely the radiating fins, thermal conductor,and sealing substrate, thus forming a sealing substrate 33 that isequipped with radiating fins. This permits a more compact configuration.

[0126] The cooling-body depicted in FIG. 7 also integrates the threemembers, that is, the radiating fins, thermal conductor, and sealingsubstrate, as in the configuration depicted in FIG. 6, yielding asealing substrate 33 that is equipped with radiating fins, but havingthe center portion CT of the heat-radiating surface of the radiating finunit mounded toward the outside, so as to gain extra surface area, whileretaining the waveform shape. The purpose of this configuration is tofurther enhance cooling at the center of the surface of the planar lightemitting layer formed by the organic EL element, where the level of heatgenerated is known to be higher.

[0127] A third embodiment is now described with reference to FIG. 8through 11. This embodiment pertains to a replacement structure forlight emitting units using organic EL elements. The liquid crystalprojector diagramed in FIG. 8 is configured as a rear-projecting tripleliquid crystal projector. It comprises three liquid crystal panels 12R,12G, and 12B, at the back of each of which is provided a light emittingunit 13R (13G, 13B) that can be freely attached or detached, to the backof which light emitting unit 13R a cooling body 34R (34G, 34B) isintegrally bonded. This cooling body 34R (34G, 34B) is configured asdescribed above with reference to FIG. 6, except that the size of thebonded area is formed 60 as to be slightly smaller than the area of theback surface of the light emitting unit 13R (13G, 13B). Around the edgethat remains on the back side of the light emitting unit 13R (13G, 13B)is bonded a board 35, as depicted in FIG. 8, 10, and 11. This board 35functions as a guided member during installation or replacement, as willbe described below, and it also functions through its lower edge to makean electrical connection with the power supply circuit.

[0128] This liquid crystal projector also comprises pairs of concaveguides 36 and 36 that are positioned on a base (not shown), in mutualopposition, for the purpose of guiding the boards 35, that is, the setsconsisting of a light emitting unit and a cooling body, in the verticaldirection. The positions of these guides 36 and 36 on the base areestablished so that, when a board is plugged in, the light emitting unit13R (13G, 13B) is positioned accurately in proximity to the back side ofthe liquid crystal panel 12R (12G, 12B), and so that the optical axisfrom the light emitting unit to the liquid crystal panel is accuratelyestablished and made straight. At positions on the base that are betweeneach pair of guides 36 and 36 are provided connectors 37, as depicted inFIG. 9. The configuration allows a plug 35L (cf. FIGS. 10 and 11) formedintegrally in the lower end of each of the boards 35 to be inserted intothe connector 37, so that it can be freely advanced or retracted. On oneside of the plug 35L is mounted a terminal TN comprising a printedcircuit for signal and power transmissions to the light emitting unit13R (13G, 13B). Hence, when a base 35 (that is, a combination of a lightemitting unit and a cooling body) is plugged into the connector 37 whileguided by the guides 36 and 36, electric power and signal circuits (notshown) are electrically connected to the light emitting unit 13R (13G,13B). Other than this, the configuration and functionality are similarto those of the embodiments described earlier.

[0129] Thus when it is judged that the light-emitting performance of alight emitting unit 13R, 13G, or 13B has fallen below allowable limits,and that its useful life has expired, or when maintenance or inspectionsare performed, any individual light emitting unit can be readilyreplaced. During replacement, only the old light emitting unit is pulledout, together with its board 35, and a new light emitting unit can besmoothly plugged in using the guide functions of the board 35 and theguides 36 and 36. Hence each light emitting unit can be easily replaced,maintenance and inspection tasks are made less tedious andtime-consuming, and any light emitting unit can be replacedindividually, which contributes to reducing maintenance and inspectioncosts as well as component costs.

[0130] In particular, in a color-displaying triple liquid crystalprojector, wherein light emitting units are installed in each of thethree liquid crystal projectors, the number thereof becomes large. Bybeing able to make replacements easily, however, one may avoid or reducethe number of occasions of unstable or poor display quality whenprojectors are driven despite a breakdown in display color balance.

[0131] Electrical connections with the light emitting units are safelysecured after replacement, of course, and, thanks to the accurateguidance of the guides 36 and 36, light emitting units are easily andaccurately restored to their proper optical positions after replacement.The orientation and positioning of the replaced light emitting units arenot altered from what they were prior to replacement, so the way inwhich light is incident on the liquid crystal panels is also unaltered,making it possible to effect high display quality and stability.

[0132] In addition, the shapes of the boards that serve as guidedmembers and the guiding members described in the foregoing, as well asthe way these are put together, can be variously altered within thescope of the intent of the present invention.

[0133] A fourth embodiment is now described with reference to FIG. 12and 13. This embodiment concerns an improvement in the directionality ofthe light emissions from the light emitting units in which organic ELelements are used.

[0134] The liquid crystal projector to which this embodiment pertainsemploys the optical arrangement diagrammed in FIG. 12 and 13. thisoptical arrangement may be employed in a triple liquid crystal projectorsuch as described in the foregoing, or it may be employed in a singleliquid crystal projector.

[0135] According to the optical arrangement diagrammed in FIG. 12 and13, a lens array 41 is interposed, as directionality regulating means,between the liquid crystal panel 12R (12G, 12B) and the light emittingunit 13R (13G, 13B) that employs an organic EL element. A plurality ofmicrolenses 41 a is formed two-dimensionally on the light-incident sideof the lens array 41, which is to say on the incident surface on theside of the light emitting unit. This plurality of microlenses 41 a isformed such that the pitch therein, respectively, is in a ratio of 4.5:1relative to the pixel pitch in the liquid crystal panel 12R (12G, 12B),and the array is optimized so that moire either does not occur or is notprominent and is exceedingly fine.

[0136] To express this quantitatively, if the focal length of themicrolens is approximately 1 mm, roughly coinciding with the lightemitting layer of the light emitting units, and the pixels in the liquidcrystal panel are of a size P (where P=33 μm, for example), then theradius of curvature of the microlenses 41 a should be approximately 500μm, and the lens pitch should be 4.5 P (150 μm, for example); that is tosay, a curvature and lens pitch in this neighborhood are desirable. Forthis reason, the light emitted from the light emitting unit 13R (13G,13B), used as a planar light source, will contain a considerablequantity of randomly oriented light components. The directionality ofthese light components is regulated by the microlenses 41 a of the lensarray 41, however, and ideally most of them strike the liquid crystalpanel 12R (12G, 12B) as more or less parallel light beams. Accordingly,most of the light emitted from the light emitting unit 13R (13G, 13B)will be incident on the liquid crystal panel 12R (12G, 12B) with goodefficiency and little waste. This prevents degradation in the brightnessof the display screen. Looking at this from another angle, by themeasure that light strikes the liquid crystal panels with paralleldirectionality and good efficiency, the less light-emitting power willbe needed in the organic EL elements, which means precisely thatdegradation in light-emitting performance due to heat generation, whichis to say the shortening of their useful life, can be prevented.*

[0137] Furthermore, among the light emitted from the light emitting unit13R (13G, 13B) or the light incident upon the lens array 41, there willbe some portion of the light components (cf. arrow a in FIG. 12) thatwill be totally reflected by the surface of the lens array 41, either onthe light-incident side or the light-emission side, due to thecontribution of the microlenses 41 a.

[0138] When these totally reflected light components return to the lightemitting unit 13R (13G, 13B), they are reflected in turn by thereflective electrode layer of the light emitting unit, and thus recycledas light that is incident upon the lens array 41. For this reason, thedeployment of the lens array 41 also further enhances the efficiencywith which the light emitted from the light emitting unit is utilized.

[0139] A modified form of this fourth embodiment is diagrammed in FIG.14 and 15. With the optical arrangement employed in this modified form,a prism array 41 is interposed as directionality regulating means, asdiagrammed, instead of a lens array. This prism array 42 has a pluralityof microprisms 42 a formed two-dimensionally on its incident side. Aswith the lens array, it is desirable that the size, height to apex, andpitch, etc., of the microprisms 42 a be established so that there isvery little total reflection of incident light by the boundary surfacesthereof, and so that, to the extent possible, parallel light is emittedtoward the liquid crystal panels. By these means the operationaleffectiveness gained is similar to what is gained when the lens arraydescribed earlier is used.

[0140] A fifth embodiment will now be described, with reference to FIG.16 and 17. This embodiment concerns improving the efficiency of lightemissions from light emitting units using organic EL elements.

[0141] The liquid crystal projector to which this embodiment pertainsemploys the light emitting unit diagrammed in FIG. 16. This lightemitting unit may be employed in a triple liquid crystal projector, orit may be employed in a single liquid crystal projector.

[0142] The light emitting unit diagrammed in FIG. 16 comprises a glasssubstrate 43 as the transparent substrate, a light emitting filmstructure LT (consisting of a transparent electrode layer 21, a lightemitting layer 22, and a reflective electrode layer 23) laminated on theglass substrate 43. In this configuration, on the emission surface onthe light-emission side of the glass substrate 43 is formed a lens arraystructure in which multiple dome-shaped lenses 43 a are arrangedtwo-dimensionally. The pitch of this multiple lens array is optimized sothat it is extremely fine, and so that the emitted light is emitted, tothe extent possible, without complete reflection (cf. arrow A in thefigure). To express this quantitatively, when in the lens arraystructure the thickness of the glass substrate 43 is 1 mm and the pixelpitch for the liquid crystal panel is P (where P=33 μm, for example),the radius of curvature of the lens 43 a should be 330 μm and the lenspitch 4.5 P (150 μm, for example); that is to say, a curvature and lenspitch in this neighborhood are desirable.

[0143] Hence, with this lens array structure, for the light emitted withthe entirety of the light emitting layer 22 as a planar light source(the way in which light is emitted is represented only in part in FIG.16, for-the sake of clarity), there will be little total reflection overthe whole surface, as compared to the case of a glass substrate 20having a flat light-incident surface as diagrammed in FIG. 17. In otherwords, the efficiency with which light is emitted toward the liquidcrystal panel 12R (12G, 12S) will be sharply increased. Hence there willbe less waste in the light that is emitted, brightness will be high, abright screen picture is obtained, and display quality can be enhanced.

[0144] It is also conceivable to form one large dome-shaped lens overthe entire light-emission surface of the glass substrate 43 in FIG. 16.That would be disadvantageous, however, in that the substrate wouldbecome quite thick at the middle of the substrate surface, without totalreflection being all that much reduced. Thus the lens array structuredescribed above is more suitable to the present invention.

[0145] A modified form of this fifth embodiment is diagrammed in FIG.18. In this modified form, a microprism array 43 b is employed insteadof the microlens array 43 a. The light emitting unit in this modifiedform also comprises a glass substrate 43 as the transparent substrate,and a light emitting film structure LT (consisting of a transparentelectrode layer 21, a light emitting layer 22, and a reflectiveelectrode layer 23) laminated on the glass substrate 43.

[0146] In this configuration, a prism array structure in which multipletriangular prisms 43 b are arranged two-dimensionally is formed on thelight-emission surface on the light-emission side of the glass substrate43. The pitch in this multiple-prism array is optimized so that it isextremely fine and so that, to the extent possible, emitted light canemerge without being totally reflected. Accordingly, the modified formof the fifth embodiment represented in FIG. 18 yields the same sort ofemission efficiency as the structure diagrammed in FIG. 17.

[0147] A sixth embodiment will now be described, with reference to FIGS.19 to 21. This embodiment concerns a projection display apparatus thatcomprises light emitting units which employ organic EL elements andaccommodate resonator structures, and it also concerns improving therebyboth the directionality of the light emitting units themselves and thespectrum waveform. In the liquid crystal projector to which thisembodiment pertains, as diagrammed in FIG. 19, a light emitting unit 13R(13G, 13B) is positioned separately on the back side of the liquidcrystal panel 12R (12G, 12B). The light emitting units 13R, 13G, and13B, unlike those described earlier, comprise resonator structures,which latter have been under intense development in recent years.Examples of such resonator structures that are known include thosedisclosed in Technical Report OME 94-79 of the Institute of Electronics,Information and Communications Engineers (IEICE).

[0148] More specifically, the light emitting units 13R, 13G, and 13B,respectively, are formed by laminating, onto a glass or othertransparent substrate 50, a half-mirror layer 51 consisting of adielectric multi-layer film, a spacer layer 52 consisting of atransparent dielectric film such as SiO₂, a transparent electrode layer53 consisting of a transparent electrically conductive film such as ITO(indium tin oxide), a hole-injection layer 54 consisting of an organicthin film that contributes to electric-field light emission, a lightemitting layer 55 consisting of an organic thin film that emits light,and a reflective electrode layer 56 consisting of a metallic film, inthat order, as diagrammed in FIG. 19. In this configuration, the lightemitting film structure LT is formed from the half-mirror layer 51,spacer layer 52, transparent electrode layer 53, hole-injection layer54, light emitting layer 55, and reflective electrode layer 56.

[0149] Since a resonator is configured by the half-mirror layer 51 andthe reflective electrode layer 56, only that light emitted by the lightemitting-layer S5 having the wavelengths determined by the resonatorlength (that is, the optical distance between the half-mirror layer 51and the reflective electrode layer 56) is resonated and emitted to theoutside with good efficiency. This emitted light becomes the light thatilluminates the liquid crystal panels 12R, 12G, and 12B. Almost none ofthe light components of other wavelengths are emitted to the outside.

[0150] The resonator length that determines the light emissionwavelength in the middle of the spectrum can be changed by altering thethicknesses of the spacer layer 51 and transparent electrode layer 53.The resonator length and light emitting layer material, etc., areoptimized according to which color the center light-emission wavelengthis set to, that is, whether red, green, or blue.

[0151] In FIG. 20 are plotted spectrum waveforms obtained both whenproviding and when not providing the light emitting unit 13R (13G, 13B)with the resonator structure, as published in Applied Physics Letters,Vol. 68, pp. 2633-2635 (1996).

[0152] Compared to the curve “without resonator structure,” the curve“with resonator structure” exhibits a narrower half band width and asharper peak. Therefore, by employing the resonator structure in thelight emitting unit 13R (13G, 13B), one can enhance the purity of thelight (i.e. light of red, green, or blue color, respectively) emittedfrom the light emitting unit itself. Hence the quantity of superfluouswavelength components outside of the desired wavelength is reduced, andhigh-quality color displays are made possible.

[0153]FIG. 21, which appeared in the same publication, plots thedirectionality both when providing and when not providing the lightemitting units 13R, 13G, and 13B with the resonator structure. Comparedto the directionality “without resonator structure,” the directionality“with resonator structure” is sharper in the direction of the frontsurface of the light source. For this reason, by providing the resonatorstructure, it is possible to obtain pictures of high frontal brightness.

[0154] A seventh embodiment will now be described, making reference toFIGS. 22 to 26. This embodiment concerns a mechanism for judgingdegradation in light emitting units that employ organic EL elements.

[0155] It is known that a light emitting unit which employs an organicEL element will gradually deteriorate, as a natural phenomenon, as thetotal time that it has been driver accumulates, and that the brightnessthereof will gradually decline. This decline is representedqualitatively in FIG. 22. When brightness is plotted against drive time,with both the vertical and horizontal axes graduated logarithmically, asin FIG. 22, the decline becomes roughly linear. Moreover, since thelight emitting layer structure of the organic EL element is ordinarilydriven with a constant current, the relationship between drive time andthe voltage on the terminals of the light emitting layer structure canbe represented qualitatively as in FIG. 23. In other words, as the drivetime increases and degradation advances, the terminal voltage graduallyincreases. The exact way in which these property trends plotted in FIG.22 and 23 change will differ according to the organic material used(i.e. the color of light emitted).

[0156] The qualitative relationship between light-emission brightnessand the current applied to the organic EL element light emitting filmstructure is plotted in FIG. 24. When this plot is made on vertical andhorizontal axes graduated logarithmically, as in FIG. 24, thelight-emission brightness will be seen to increase roughly linearlyrelative to the current.

[0157] In view of these circumstances, in the liquid crystal projectorthat is the projection display apparatus to which this embodimentpertains, the measurement and control circuitry diagrammed in FIG. 25 isconnected to the light emitting unit 13R (13G, 13B). A constant-currentsupply 60 is connected between the electrodes of the light emitting filmstructure LT of the light emitting unit 13R (13G, 13B), providing aconstant-current drive. This constant-current source 60 is made so thatthe constant-current value can be altered by control signals.

[0158] A voltmeter 61 is connected in order to measure the terminalvoltage between these electrodes. Measurement signals from thisvoltmeter 61 are converted to digital values by an A/D converter 62, andinput to a CPU 63. To the CPU 63 is connected both a LED 64 thatnotifies when it is time to replace a light emitting unit and a D/Aconverter 65. The CPU 63 performs the processing diagrammed in FIG. 26,turning the LED 64 on and off, while, at the same time, sending controlsignals via the D/A converter 65 to the constant-current source 60 so asto control the constant-current value. One example of a controloperation of the CPU 63 is now described with reference to FIG. 26. Thiscontrol operation is executed at set time intervals for each color, by,for example, an interrupt routine once every hour.

[0159] The CPU 63 first reads in the measured voltage value from thevoltmeter 61 via the A/D converter 62 (step S1). Then, referencing atable for the curve shown in FIG. 23, it performs a reverse computationto find the cumulative value of the drive time that corresponds to thevoltage value measured (step S2). Next, referencing a table for thecurve shown in FIG. 22, it performs a reverse computation to find thebrightness B corresponding to the cumulative value of the drive time(step S3).

[0160] Next the CPU 63 determines whether or not the brightness B sofound is equal to or still exceeds a preset allowable brightness valueB0 (step S4). If the answer is NO, that is, if B<B0, then the brightnesshas fallen below the allowable value and the color pictures havedarkened, so the LED 64 will be immediately lighted, giving notice thatit would be better to replace the light emitting unit (step S5).

[0161] Conversely, if the answer in step S4 is YES, then the CPU 63judges whether or not the color balance between red, green, and blue isas set, based on brightness values for the three colors (step S6). Whenthe color balance is not as set (NO), then the CPU 63 does a reversecomputation to determine the value of the drive current needed to obtainthe desired brightness, referencing a table for the curve plotted inFIG. 24 (step S8). Having done that, it sends control signals forobtaining that drive current value to the constant-current source 60 viathe D/A converter 65. In this way, the value of the drive current iscorrected, and the desired brightness value for the color handled by thelight emitting unit 13R (13G, 13B) is obtained.

[0162] By monitoring the voltage on the terminals of the light emittingunits in this manner, notification can be made, automatically andaccurately, when it is time to replace the light emitting units, makingmaintenance easier, and providing a continually bright picture. Inaddition, the color balance is automatically corrected from the terminalvoltage value, thus providing a continually stable and high-qualitypicture. In the processing diagrammed in FIG. 26 and described in theforegoing, the reverse computations pertaining to FIG. 22 through 24need not necessarily reference tables; instead, the configuration may bemade so that values are found by calculating from the approximate curve(straight line). An even simpler technique may also be used, wherein,without exactly finding the brightness value, the cumulative drive timesum is found from the terminal voltage value, which cumulative sum iscompared against limiting values of drive times determined throughexperience, enabling the useful life of the light emitting layer to bedetermined more expediently from the comparison results.

[0163] Moreover, it is also permissible to combine and implement, asexpedient, some of the configurations and means of the severalembodiments described in the foregoing, and thereby further enhance thevarious benefits described in the foregoing, such as achieving smallersizes and lighter weights in the overall liquid crystal projector,obtaining pictures of high brightness, and simplifying maintenance andinspection operations.

[0164] An eighth embodiment will now be described, making reference toFIG. 27. This embodiment-concerns a light source and a method andapparatus for controlling the light source. FIG. 1 is a simplifiedcross-sectional view of the configuration of the light source.

[0165] A light emitting unit 100 is configured such that a transparentelectrode film 102 that forms the anode, an organic light emitting layer103, and a metallic electrode film 104 that forms the cathode aresequentially laminated onto a glass substrate 101, and this is sealedwith a sealing substrate 105. The planar size of this light emittingunit 100 will depend on the object that is to be illuminated, but itmay, for example, be made on the order of 30 mm×25 mm. The sealingsubstrate 105 of the light emitting unit 100 is provided with a heatsink 106 with an intervening layer of grease 109 exhibiting good thermalconductivity. To the heat sink 106 is attached, across anotherintervening layer of grease 109 exhibiting good thermal conductivity, aflat-panel-shaped electronic cooling element 107 which utilizes thePeltier effect. The sealing substrate 105 that configures the lightemitting unit 100 may also do double duty as the heat sink 106. Theelectronic cooling element 107 is air-cooled by a fan 108.

[0166] A thermocouple is imbedded into the heat sink 106 to serve as atemperature sensor 110 to measure the temperature of the heat sink.Something other than a thermocouple, such as a thermistor, may be usedas the temperature sensor 110. Also, the temperature sensor may beattached to the heat sink instead of being imbedded in it.

[0167] A temperature switch circuit can drive and control both alighting switch 112 for lighting and extinguishing, and a cooling switch114 for supplying or cutting off current to the electronic coolingelement 107. The positive terminal of a DC power source 113 is connectedto the transparent electrode, while the negative terminal thereof isconnected via the lighting switch 112 to the metal electrode film 104.The positive electrode of a DC power supply 115 is connected directly tothe electronic cooling element 107 while the negative terminal thereofis connected via the cooling switch 114 to the electronic coolingelement 107.

[0168] When DC voltage from the DC power supply 113 is applied to thetransparent electrode film 102 and the metal electrode film 104, theorganic light emitting layer 103 emits light, and the emitted light 116is radiated toward a glass substrate 101. The organic light emittinglayer 103 may be a single layer or it may have a laminar structure madeup of an electron-transport carrying layer consisting of an organicfilm, and an organic light emitting film.

[0169] A method of controlling the light source apparatus is nextdescribed.

[0170] First is described a procedure for lighting an organic EL planarlight source for illuminating the body to be illuminated.

[0171] Before lighting the light emitting unit 100, the electroniccooling element 107 is first activated by closing the cooling switch114. The electronic cooling element 107, thereupon, driven by the DCpower supply 115, gradually cools the heat sink 106 and the lightemitting unit 100.

[0172] The temperature of the heat sink 106 is monitored by thetemperature sensor 110. At the point in time when the heat sink reachesa certain set temperature, say 10° C., for example, the lighting switch112 for the organic EL planar light source is closed by the temperatureswitch circuit 111.

[0173] By closing the lighting switch 112, electric power is supplied tothe light emitting unit 100 from the DC power source 113, and the lightemitting unit 100 radiates light.

[0174] If the light emitting unit 100 is lighted before it has beenadequately cooled, there will be a pronounced rise in the temperature ofthe organic EL element, and the organic EL element will begin to degradein a short time, with its brightness declining.

[0175] If, on the other hand, the organic EL element is excessivelycooled, dew will form on the front and side surfaces of the organic ELelement. This dew will alter the radiation pattern of the emitted light,and cause changes in the properties of the organic film which arereadily altered by moisture. When the organic EL element is lighted,even it the light emitting unit 100 is being cooled by the electroniccooling element 107, the temperature of the organic EL element will, dueto the heat generated by the organic EL element, reach a steady state ata temperature that is higher than the temperature of the heat sink 106,so that no dew forms on the light source.

[0176] Next is described a procedure for extinguishing the organic ELplanar light source in order to stop illuminating the body beingilluminated.

[0177] First of all, the current being supplied to the organic lightemitting layer 103 configuring the light emitting unit 100 is reduced,lowering the brightness of the light being emitted. Almostsimultaneously with lowering the brightness of the emitted light, thecooling switch 114 is opened, stopping the supply of power to theelectronic cooling element 107 and so terminating cooling.

[0178] At this time, the current flowing through the organic lightemitting layer 103 need only be enough to make the organic lightemitting layer shine slightly; the light emitting unit 100 need onlygenerate enough heat to keep dew from forming on its surface.

[0179] If, at this juncture, a large current is passed through theorganic light emitting layer 103, the temperature of the light emittingunit 100 will rise because the cooling has been terminated, so that, asa result, functional degradation of the light source will beaccelerated.

[0180] At the point in time where the temperature of the heat sink 106has risen to a certain set temperature, say 10° C., for example, thelighting switch 112 is opened, terminating the supply of current to theorganic light emitting layer 103, and extinguishing the organic ELelement.

[0181] When, instead of implementing the procedure just described, thelight emitting unit 100 is extinguished simultaneously with terminatingthe electronic cooling element 107, the heat sink 106 will still becold, and the generation of heat by the light emitting element 100 hasbeen terminated, so the organic EL element will be chilled and dew willform on it.

[0182] Instead of the grease 109 that is interposed between the heatsink 106 and the sealing substrate 105 of the light emitting unit 100 inthe light source configuration in this embodiment, it is possible tointerpose a sheet exhibiting high thermal conductivity. When this isdone, it becomes easy to remove the organic EL planar light source 100from the heat sink 106, thus making it easy to replace the organic ELplanar light source 100.

[0183] A ninth embodiment will now be described, making reference toFIG. 28. This embodiment concerns the application of the eighthembodiment to a projection display apparatus. FIG. 28 is a simplifiedcross-sectional view of the main optical systems that configure aprojection display apparatus. With respect to this projection displayapparatus, configurational elements that are the same as or similar tothose explained in connection with the first embodiment are indicated bythe same reference characters, while, with respect to the apparatus forimplementing the control method for the light source apparatus, thoseconfigurational elements that are the same as or similar to thoseexplained in connection with the eighth embodiment are indicated by thesame reference characters, and the description thereof is either omittedor abridged. The same applies to descriptions for the tenth andsubsequent embodiments herein.

[0184] The images displayed on the red-displaying liquid crystal panel12R that displays red component images, on the green-displaying liquidcrystal panel 12G that displays green component images, and on theblue-displaying liquid crystal panel 12B that displays blue componentimages are combined by the dichroic prism 15, then enlarged by theprojection lens 16 and displayed on the screen 17.

[0185] In the interest of clarity, the structures of the liquid crystalpanels and projection lens are not drawn, but those components aredepicted as blocks. Either a reflective or a transmissive screen can beemployed for the screen 17.

[0186] The red-displaying liquid crystal panel 12R is illuminated by ared-light emitting unit 100R that emits red light and that is positionedat its back. The light emitting unit 100R has the structure diagrammedin FIG. 27, for example, and is cooled by a cooling mechanism thatcomprises a heat sink 106, electronic cooling element 107, and fan 108,as shown in the same FIG. 27. In FIG. 28, in the interest of clarity,the grease, temperature sensor, and temperature switch circuit depictedin FIG. 28 are omitted, but the control method described in connectionwith the eighth embodiment is used to start and stop the electroniccooling element 107, and to control the lighting and extinguishing ofthe organic EL planar light source.

[0187] Similarly, for the green-displaying liquid crystal panel 12G andthe blue-displaying liquid crystal panel 125, a green-light emittingunit 100G that emits green light is positioned at the back of thegreen-displaying liquid crystal panel 12G, and a blue-light emittingunit 100B that emits blue light is positioned at the back of theblue-displaying liquid crystal panel 12B, and the respective organic ELplanar light sources therefor are cooled by a cooling mechanism like theone described in connection with the eighth embodiment.

[0188] A tenth embodiment will now be described, making reference toFIG. 29. This embodiment concerns a light source and a method andapparatus for controlling the light source. FIG. 29 is a simplifiedcross-sectional view of the configuration of the light source.

[0189] Except insofar as the position of the temperature sensor 110 isdifferent than it is in the configuration of the light source in theeighth embodiment diagrammed in FIG. 27, all of the configurationalelements are the same.

[0190] The temperature of the light emitting unit 100 is detected by thetemperature sensor 110, and a temperature switch circuit 111 is providedwhich, in response to that temperature, controls either the lightingswitch 112 for the light emitting unit 100 or the cooling switch 114 forthe electronic cooling element 107.

[0191] The light source control method is described next.

[0192] First, the procedure used when lighting the organic EL element inorder to illuminate the body to be illuminated is described.

[0193] Before lighting the light emitting unit 100, the electroniccooling element 107 is first activated. The electronic cooling element107 is driven by the DC power supply 115, whereupon it gradually coolsthe heat sink 106 and the light emitting unit 100.

[0194] The temperature of the light emitting unit 100 is monitored bythe temperature sensor 110. When the temperature of the light emittingunit 100 reaches a certain set temperature, say 10° C., for example, thelighting switch 112 is closed by the temperature switch circuit 111.

[0195] By closing the lighting switch 112, power is supplied from the DCpower supply 113 to the light emitting unit 100 and the light emittingunit 100 radiates light.

[0196] Next is described a procedure for extinguishing the organic ELelement in order to stop illuminating the object being illuminated.

[0197] First of all, the current being supplied to the organic lightemitting layer 103 configuring the light emitting unit 100 is reduced,lowering the brightness of the light being emitted. Almostsimultaneously with lowering the brightness of the emitted light, thecooling switch 114 is opened, stopping the supply of power to theelectronic cooling element 107 and so terminating cooling. At this time,the current flowing through the organic light emitting layer 103 needonly be enough to make the organic light emitting layer shine slightly;the organic EL element need only generate enough heat to keep dew fromforming on the surface of the light emitting unit 100.

[0198] After cooling has been terminated, the heat sink 106 will stillbe cooling the light emitting unit 100 for a little while, but when thetemperature of the heat sink 106 begins to rise, the temperature of thelight emitting unit 100 will also begin to rise.

[0199] At the point in time when the temperature of the light emittingunit 100 has risen to a certain set temperature, say 10C, for example,the lighting switch 112 will be opened, the supply of current to theorganic light emitting layer 103 will be stopped, and the organic ELelement will be extinguished. In the eighth and tenth embodiments, thetemperature sensor was attached either to the heat sink or to theorganic EL element, that is, to only one of the two. It is alsopossible, however, to attach it to both, and thus, while monitoring thetemperatures of both the heat sink and the organic EL element, tocontrol the timing of the initiation and termination of cooling, and oflighting and extinguishing the organic EL element.

[0200] An 11th embodiment will now be described. This embodimentconcerns the application of a control apparatus for a light sourceapparatus in a projection type liquid crystal display apparatus.

[0201] In other words, the 11th embodiment is the application of thetenth embodiment to a projection display apparatus.

[0202] A 12th embodiment will now be described, making reference to FIG.30. This embodiment concerns a light source and a method and apparatusfor controlling the light source. FIG. 30 is a simplifiedcross-sectional diagram of the configuration of a light source.

[0203] In this configuration, the temperature sensor 110 and thetemperature switch circuit 111 in the light source of the eighthembodiment diagrammed in FIG. 27 are removed, and in their place a timercircuit 121 is provided. The other configurational elements, that is,the light emitting unit 100, heat sink 106, electronic cooling element107, and fan 108 are the same as in the eighth embodiment.

[0204] The timer circuit 121 controls the lighting switch 112 of thelight emitting unit 100 or the cooling switch 114 of the electroniccooling element 107.

[0205] A light source control method is now described.

[0206] A procedure is first described for lighting the organic EL planarlight source in order to illuminate the object to be illuminated.

[0207] Before lighting the light emitting unit 100, the electroniccooling element 107 is first activated by closing the cooling switch114. The electronic cooling element 107 is driven by the DC power supply115, and the heat sink 106 and organic EL planar light source l00 aregradually cooled.

[0208] The timer circuit 121 begins measuring elapsed time from themoment the cooling switch 114 is closed. At the point in time when someset time has elapsed since the closing of the cooling switch 114, thelighting switch 112 that is connected to the light emitting unit 100 isclosed.

[0209] By closing the lighting switch 112, power is supplied to thelight emitting unit 100 from the DC power supply 113, and the lightemitting unit 100 radiates light.

[0210] By measuring beforehand the variation in the temperature of thelight emitting unit 100 from the start of cooling, the time that ittakes for the temperature of the light emitting unit 100 to reach acertain set temperature after the cooling switch 114 is closed can befound. Based on that time, it is possible to set the time from theclosing of the cooling switch 114 to the closing of the lighting switch112.

[0211] Next, a procedure for extinguishing the light emitting unit 100in order to stop illuminating the object being illuminated will bedescribed.

[0212] First of all, the current being supplied to the organic lightemitting layer 103 configuring the light emitting unit 100 is reduced,lowering the brightness of the light being emitted. Almostsimultaneously with lowering the brightness of the emitted light, thecooling switch 114 is opened, stopping the supply of power to theelectronic cooling element 107 and so terminating cooling.

[0213] At the point in time where some set time interval has elapsedsince the opening of the cooling switch 114, the lighting switch 112connected to the light emitting unit 100 is opened, and the lightemitting unit is extinguished.

[0214] By measuring beforehand the change in the temperature of theorganic EL element after the termination of cooling, it is possible todetermine the time that it takes for the organic EL element to reachsome set temperature after the opening of the cooling switch 114 and thetermination of cooling. Based on this time period, it is possible to setthe time from the opening of the cooling switch 114 to the opening ofthe lighting switch 112.

[0215] In the configuration of the light source in this embodiment,instead of the grease 109 interposed between the heat sink 106 and thesealing substrate 105 of the light emitting unit 100, it is possible tointerpose a sheet exhibiting high thermal conductivity. When that isdone, it becomes easy to remove the heat sink 106 from the lightemitting unit 100, making it easy to replace the light emitting unit100.

[0216] A 13th embodiment will now be described. This embodiment concernsthe application of the 12th embodiment to a projection displayapparatus.

[0217] In the 13th embodiment, in other words, an example is describedwherein the 12th embodiment is applied to the projection displayapparatus diagrammed in FIG. 28.

[0218] In the foregoing, descriptions have been given for the lightsource apparatuses and for the methods and apparatuses for controllingthe light source apparatuses of the present invention, together withdescriptions of display apparatuses in which those control methods andapparatuses are applied. It is possible to conceive of many differentconfigurations and control methods for shifting the timing of thelighting of the light source apparatus and the timing of cooling inorder to sufficiently cool the organic EL elements while suppressing theformation of dew on the organic EL elements, which is a main object ofthe present invention. For example, one can conceive of a configurationand control method wherein both a timer circuit and a temperature switchcircuit are provided, wherein the temperature switch circuit is employedwhen lighting an organic EL element and the timer circuit is employedwhen extinguishing it.

[0219] It is also possible to provide a humidity sensor, and to varyeither the set temperature or the set time according to the humidity.

[0220] The industrial potential of the present invention will now bediscussed.

[0221] By implementing the projection display apparatus of the presentinvention, as described in the foregoing, it is possible to employorganic EL elements as light emitting layers, to provide cooling meanstherefor, attachment means permitting free attachment and detachment,means for regulating the directionality of the emitted light, means forraising the efficiency of the emitted light, and means for automaticallydetermining the useful life, and to employ a resonator structure,wherefore a projection display apparatus can be provided in which lightemitting units based on organic EL elements are employed, which is lightin weight, small in size, and capable of practical implementation, andwhich overcomes problems that are very difficult to overcome with theprior art.

[0222] In particular, by installing cooling means comprising electroniccooling elements or heat-radiating fins in the light emitting units, itis possible to suppress degradation in light-emission performance causedby heat generated by the organic EL elements, thereby extending usefullife, stabilizing brightness, and continually securing maximumbrightness.

[0223] Also, by providing attachment means for attaching the lightemitting units to the base on which the liquid crystal panels and lightemitting units are mounted, so that they may be freely attached ordetached, it is possible to make the light emitting units comprisingorganic EL elements to be individually independent, and to easilyreplace them in conditions wherein their electrical connections andoptical positions are definitely secured. Thus the replacement operationis made more efficient and maintenance and inspection are simplified.

[0224] Furthermore, by measuring the terminal voltage across theelectrodes of the light emitting film structure, determining the lifeexpectancy of the light emitting film structure from that terminalvoltage value, and, when the useful life is judged to have expired,announcing that fact, it is easy to determine when it is time to replacethe light emitting units, and thereby to insure high quality picturedisplays and facilitate maintenance and inspection.

[0225] Moreover, by providing directionality-regulating means such aslens arrays or prism arrays to regulate the directionality of the lightemitted from the light emitting units so that it faces the liquidcrystal panels, the directionality of the light incident on the liquidcrystal panels from the light emitting units comprising organic ELelements can be improved, the efficiency of light incidence on theliquid crystal panels can be enhanced, and pictures exhibiting highstabilized brightness can be presented.

[0226] Furthermore, by integrally forming microlens arrays or microprismarrays on the light-emission surfaces of the transparent substrates ofthe light emitting units, it is possible to raise the light-emissionefficiency from the light emitting units comprising organic EL elements,and thus to present pictures exhibiting high stabilized brightness.

[0227] Moreover, by providing, in the light emitting layer structures ofthe light emitting units, resonator structures that selectively resonateand emit light of specific wavelengths, the directionality andefficiency of light incident on the liquid crystal panels can be sharplyimproved.

[0228] The light source apparatuses according to the present inventioncomprise organic EL elements and cooling mechanisms for cooling them,and either temperature sensors attached to the organic EL elements or tocooling means, or, alternatively, timers, so that the organic ELelements can be controlled in a cooled state using the cooling means.

[0229] The method of controlling the light source apparatus of thepresent invention, furthermore, is characterized by the fact that thetiming both of cooling starting and stopping and of lighting andextinguishing the organic EL planar light sources is shifted, either bymonitoring the temperature of the organic EL elements with temperaturesensors, or by means of timers. Thus it is possible to sufficiently coolthe organic EL elements while suppressing the formation of dewthereupon, so that degradation in the organic EL elements can besuppressed and their useful life extended.

[0230] The control apparatus for the light source apparatus of thepresent invention, moreover, is characterized by the fact that itcontrols the timing both of cooling starting and stopping and oflighting and extinguishing the organic EL planar light sources, eitherby monitoring the temperature of the organic EL elements withtemperature sensors, or by means of timers. Thus it is possible tosufficiently cool the organic EL elements while suppressing theformation of dew thereupon, so that degradation in the organic ELelements can be suppressed and their useful life extended.

[0231] Furthermore, if the method and the apparatus for controlling thelight source apparatus of the present invention is implemented, thedisplay apparatus of the present invention can be made significantlysmaller than a display apparatus which uses an electric discharge lampas the light source.

What is claimed is:
 1. (Deleted)
 2. (Deleted)
 3. (After correction) Aprojection display apparatus comprising: transmissive liquid crystalpanels that display images; light source units that are positioned onthe back side of said liquid crystal panels and that comprise lightemitting units provided with organic EL elements as light emittinglayers and cooling means provided in said light emitting units forradiating heat generated by said light emitting units; and a projectionlens positioned in front of said liquid crystal panels for enlargingimages displayed on said liquid crystal panels and projecting them ontoa screen; wherein said cooling means comprise: cooling bodies comprisingheat-dispersing fin units that are positioned at the back of reflectiveelectrode layers positioned at the back of said light emitting layersand that guide and disperse said generated heat; sealing substrates forsealing portions of light emitting film structures containing saidreflective electrode layers; and said sealing substrates and saidcooling bodies comprise integrated structures.
 4. (After correction) Aprojection display apparatus comprising: transmissive liquid crystalpanels that display images; light source units that are positioned onthe back side of said liquid crystal panels and that comprise lightemitting units provided with organic EL elements as light emittinglayers and cooling means provided in said light emitting units forradiating heat generated by said light emitting units; and a projectionlens positioned in front of said liquid crystal panels for enlargingimages displayed on said liquid crystal panels and projecting them ontoa screen; wherein said cooling means comprise cooling bodies comprisingheat-dispersing fin units that are positioned at the back of reflectiveelectrode layers positioned at the back of said light emitting layersand that guide and disperse heat generated by said light emitting units,the surfaces of which heat-dispersing fin units are formed so that thecenters thereof exhibit greater surface area than the ends thereof. 5.(After correction) The projection display apparatus according to claim 3or claim 4 , wherein said organic EL elements are elements that generatewhite light.
 6. The projection display apparatus according to claim 3 orclaim 4 , wherein said liquid crystal panels comprise three liquidcrystal panels that separately display images in red components, greencomponents, and blue components, said organic EL elements comprisingthree organic EL elements that separately generate red, green, and bluelight, exhibiting a structure wherein a dichroic prism is interposed inthe optical path between said three liquid crystal panels and saidprojection lens.
 7. A projection display apparatus comprising;transmissive liquid crystal panels that display images; light emittingunits positioned in back of said liquid crystal panels and provided withlight emitting layers comprising organic EL elements; and attachmentmeans for attaching said light emitting units, such that they can befreely attached and detached, to at least the portions of a base onwhich are mounted said liquid crystal panels and said light emittingunits.
 8. The projection display apparatus according to claim 7 ,wherein said light emitting units comprise: boards that mount bothelectrode layers that sandwich said light emitting layers and terminalsthat are electrically connected to said electrode layers, while saidattachment means comprise both connectors that plug terminal units intosaid base portions, such that they can be freely plugged and unplugged,said terminal units having mounted in them the terminals of said boards,and guides that guide said boards in the direction of connector plug-in,when said terminal units of said boards are inserted into saidconnectors.
 9. The projection display apparatus according to claim 7 ,comprising: light source units which comprise cooling leans forradiating heat generated by said light emitting layers; and lightemitting units containing said light emitting layers.
 10. The projectiondisplay apparatus according to claim 9 , wherein said cooling meanscomprise heat-radiating fins that are provided on the back side ofreflective electrode layers positioned at the back of said lightemitting layers, which conduct and radiate said generated heat.
 11. Aprojection display apparatus comprising: transmissive liquid crystalpanels that display images; and light emitting units, positioned at theback of said liquid crystal panels; light emitting layer structureshaving light emitting layers made up of organic-EL elements are providedon transparent substrates; means for raising the light-emissionefficiency are formed integrally on the light emitting surfaces of saidtransparent substrates of said light emitting units.
 12. The projectiondisplay apparatus according to claim 11 , wherein said means for raisinglight-emission efficiency are microlens arrays formed two-dimensionallyon said light-emission surfaces.
 13. The projection display apparatusaccording to claim 11 , wherein said means for raising light-emissionefficiency are microprism arrays formed two-dimensionally on saidlight-emission surfaces.
 14. A projection display apparatus comprising:light emitting units positioned at the back of liquid crystal panels andhaving light emitting film structures, the light emitting layers ofwhich are organic EL elements, provided on transparent substrates;voltage measuring means for measuring voltages on terminals betweenelectrodes of said light emitting film structures; useful-lifeassessment means for assessing useful life remaining in said lightemitting film structures; and announcement means for announcing saiduseful life when said useful-life assessment means have assessed saiduseful life.
 15. The projection display apparatus according to claim 14, wherein said useful-life assessment means are means for assessing saiduseful life by converting said terminal voltage values to brightnessvalues and comparing these against reference values.
 16. The projectiondisplay apparatus according to claim 14 , comprising: color-balanceassessment means for assessing red, green, and blue color balance onbasis of terminal voltage values measured by said voltage measuringmeans, and color-balance correction means for automatically correctingcolor balance on basis of results of assessment by said color-balanceassessment means.
 17. The projection display apparatus according toclaim 1 , 2 , 3, or 4, wherein said light emitting structure for saidlight emitting units comprises a resonator structure that selectivelyresonates and emits light of a particular wavelength.
 18. A light sourceapparatus comprising: light source units comprising light emitting unitsprovided with organic EL elements as light emitting layers and coolingmeans provided in said light emitting units for radiating heat generatedby said light emitting units; and temperature detection means formeasuring temperature of said cooling means.
 19. A light sourceapparatus comprising: light source units comprising light emitting unitsprovided with organic EL elements as light emitting layers and coolingmeans provided in said light emitting units for radiating heat generatedby said light emitting units; and temperature detection means formeasuring temperature of said organic EL elements.
 20. A light sourceapparatus comprising: light source units comprising light emitting unitsprovided with organic EL elements as light emitting layers and coolingmeans provided in said light emitting units for radiating heat generatedby said light emitting units; and at least one or other of elapsed timemeasuring means for measuring elapsed time after start of said coolingmeans or elapsed time measuring means for measuring elapsed time afterstopping of said cooling means.
 21. A light source apparatus controlmethod for controlling cooling starts and lighting of a light sourcecomprising; light source units comprising light emitting units providedwith organic EL elements as light emitting layers and cooling meansprovided in said light emitting units for radiating heat generated bysaid light emitting units; and temperature detection means for measuringtemperature of said cooling means; said organic EL elements are lightedat the point in time when temperature detected by said temperaturedetection means reaches a set temperature, after said cooling means havebeen started.
 22. A light source apparatus control method forcontrolling cooling starts and lighting of a light source comprising:light source units comprising light emitting units provided with organicEL elements as light emitting layers and cooling means provided in saidlight emitting units for radiating heat generated by said light emittingunits; and temperature detection means for measuring temperature of saidorganic EL elements; said organic EL elements are lighted at the pointin time when temperature detected by said temperature detection meansreaches a set temperature, after said cooling means have been started.23. A light source apparatus control method for controlling coolingstoppages and extinguishing of a light source comprising: light sourceunits comprising light emitting units provided with organic EL elementsas light emitting layers and cooling means provided in said lightemitting units for radiating heat generated by said light emittingunits; and temperature detection means for measuring temperature of saidcooling means; wherein after reducing drive current going to saidorganic EL elements, said cooling means are stopped; and said organic ELelements are extinguished at the point in time when temperature detectedby said temperature detection means reaches a set temperature.
 24. Alight source apparatus control method for controlling cooling stoppagesand extinguishing of a light source comprising: light source unitscomprising light emitting units provided with organic EL elements aslight emitting layers and cooling means provided in said light emittingunits for radiating heat generated by said light emitting units; andtemperature detection means for measuring temperature of said organic ELelements; wherein after reducing drive current going to said organic ELelements, said cooling means are stopped; and said organic EL elementsare extinguished at the point in time when temperature detected by saidtemperature detection means reaches a set temperature.
 25. A lightsource apparatus control method for controlling cooling starts andlighting of a light source comprising: light source units comprisinglight emitting units provided with organic EL elements as light emittinglayers and cooling means provided in said light emitting units forradiating heat generated by said light emitting units; and elapsed timemeasuring means for measuring elapsed time from start of said coolingmeans; wherein said organic EL elements are lighted after a certain timehas elapsed since said cooling means were started.
 26. A light sourceapparatus control method for controlling cooling stoppages andextinguishing of a light source comprising: light source unitscomprising light emitting units provided with organic EL elements aslight emitting layers and cooling means provided in said light emittingunits for radiating heat generated by said light emitting units; elapsedtime measuring means for measuring elapsed time from stoppage of saidcooling means; wherein after reducing drive current going to saidorganic EL elements, said cooling means are stopped; and said organic ELelements are extinguished a certain time thereafter.
 27. A controlapparatus for a light source apparatus that comprises; light sourceunits comprising light emitting units provided with organic EL elementsas light emitting layers and cooling means provided in said lightemitting units for radiating heat generated by said light emittingunits; and temperature detection means for measuring temperature of saidcooling means; that illuminates liquid crystal display elements withlight radiated from said organic EL elements; wherein said light sourceapparatus is controlled so that, when lighting said organic EL elements,said organic EL elements are lighted at the point in time when, aftersaid cooling means have been started, temperature detected by saidtemperature detection means reaches a set value for lighting; so that,when extinguishing said organic EL elements, said cooling means arestopped after reducing drive current going to said organic EL elements;and said organic EL elements are extinguished at the point in time whentemperature detected by said temperature detection means reaches a setvalue for extinguishing.
 28. A control apparatus for a light sourceapparatus that comprises: light source units comprising light emittingunits provided with organic EL elements as light emitting layers andcooling means provided in said light emitting units for radiating heatgenerated by said light emitting units; temperature detection means formeasuring temperature of said organic EL elements; that illuminatesliquid crystal display elements with light radiated from said organic ELelements; wherein said light source apparatus is controlled so that,when lighting said organic EL elements, said organic EL elements arelighted at the point in time when, after said cooling means have beenstarted, temperature detected by said temperature detection meansreaches a set value for lighting; so that, when extinguishing saidorganic EL elements, said cooling means are stopped after reducing drivecurrent going to said organic EL elements; and said organic EL elementsare extinguished at the point in time when temperature detected by saidtemperature detection means reaches a set value for extinguishing.
 29. Acontrol apparatus for a light source apparatus that comprises: lightsource units comprising light emitting units provided with organic ELelements as light emitting layers and cooling means provided in saidlight emitting units for radiating heat generated by said light emittingunits; elapsed time measuring means for measuring elapsed time fromstart of said cooling means; elapsed time measuring means for measuringelapsed time from stoppage of said cooling means; that illuminatesliquid crystal display elements with light radiated from said organic ELelements; wherein said light source apparatus is controlled so that,when lighting said organic EL elements, said organic EL elements arelighted after a certain time has elapsed since said cooling means werestarted; so that, when extinguishing said organic EL elements, saidcooling means are stopped after reducing drive current going to saidorganic EL elements; and said organic EL elements are extinguished acertain time thereafter.
 30. The control apparatus for a light sourceapparatus, according to claim 26 , 27 , 28, or 29, applied to aprojection type projection display apparatus that takes images displayedon said liquid crystal display elements and enlarges and projects themby a projection lens.